Following growing concern about the potential impact of the bacterium Xylella fastidiosa on the UK environment, earlier this week the Horticultural Trades Association (HTA), together with several garden retailers and growers, have coordinated an embargo on imported stock from infected areas.

The move, which is joined by a 5-point health management plan, has arisen from an industry desire to create a stronger defence to the Xyella pathogen.

What is Xyella, and why would the HTA take such measures to prevent its spread to the UK?

Xyella fastidiosa is a bacterium, which can cause disease in a particularly wide range of woody plants. It has 4 sub-species, each of which attack different plants.

It is likely Xyella fastidiosa will affect other woody plants if it arrives in the UK. The extent of this will not be known until the event, however.

The reason for the precautionary measures, is the potential harm Xyella could do to the UK environment. Xyella is responsible for large scale loses of commercial and amenity trees in USA, Italy and Brazil. In Brazil, 40% of citrus trees have been lost to the bacterium, resulting in $120 million US dollars of lost revenue to the economy.

What does Xyella do to host plants?

The disease attacks the water-conducting mechanisms of the host plant, and inhibits movement of water and nutrients. This can leads to the death of the plant.

How is Xyella spread?

Xyella is spread by insects which feed on the water-conducting mechanisms within a plant. The UK contains several species which fit into this category and, should Xyella become established in the UK, help spread it over long distances. Xyella may also be spread during the transport of plants as part of landscaping schemes.